42985: issues: simplify post() r=jordanlewis a=tbg

This prepares the code for allowing the caller more control over the
message body. This makes sense since post() is called both by roachtest
and nightly stress, and it doesn't make sense to use the same message
body for both.

Release note: None

42986: roachprod: don't try to make long dns names r=dt a=dt

long cluster names break DNS. Rather than break DNS for everyone, just skip the clusters that have these long names.
DNS is a nice-to-have in any case, so it is OK to skip it -- roachprod will fallback to IPs.

Release note: none.

42991: settings: explanatory comments around cluster settings r=irfansharif a=irfansharif

Update stale references to changed method signatures and add a bit more
documentation around the usage of IsActive.

Release note: None

42998: sql: bugfixes in role membership caching r=petermattis a=rohany

Fixes #42098.

This PR fixes some bugs in role membership caching.

* The role membership cache was a single global, which meant
  multiple servers in the same cockroach process could pollute
  the cache for each other, causing flaky test failures.
* The cache updating mechanism seemed to use the incorrect variable
  to update the cache version when a concurrent request caused a cache
  invalidation as well. Although unlikely, this could have lead to incorrect
  results being served.

Release note (bug fix): This change fixes some existing caching issues
surrounding role memberships, where users could sometimes see out of date
role membership information.

Co-authored-by: Tobias Schottdorf <tobias.schottdorf@gmail.com>
Co-authored-by: David Taylor <tinystatemachine@gmail.com>
Co-authored-by: irfan sharif <irfanmahmoudsharif@gmail.com>
Co-authored-by: Rohan Yadav <rohany@alumni.cmu.edu>